Our goal is develop a safe, in vivo human model that can translate the conflicting revelations that rapamycin (RAPA) expands lifespan in mice but yet causes endothelial dysfunction. Our pilot project will develop this new model by using local, non- invasive and minimally invasive techniques to examine the effects of local RAPA treatment in small areas of the body, obviating risks of systemic drug administration. Despite anti-aging effects, RAPA has been reported to cause endothelial dysfunction through increased oxidative and nitrosative stress, a deleterious process that leads to atherosclerosis and other human vasculopathies. Clinical studies find that RAPA eluting stents induce endothelial dysfunction and increase in-stent thrombosis risk in humans. RAPA thus appears to have long-sought anti-aging effects, but yet may have deleterious cardiovascular effects. This confusing dichotomy of effects must be explained if RAPA is to be translated safely into clinical medicine as an anti-aging therapy. Although RAPA appears to have anti-aging benefits, we hypothesize that deleterious vascular endothelium effects limits its usefulness in humans. Specific aims we will address in developing and validating our local treatment model are to define: I.the optimal concentration of RAPA in a topically applied ointment that achieves a reproducible and functionally relevant inhibition of mTOR (21, 51). II.whether interstitial superoxide, hydrogen peroxide, bioavailable NO, NADPH oxidase, and endothelial NOS levels in skin are altered by mTOR inhibition with topical treatment with RAPA ointment (13, 15, 40). III.whether mTOR inhibition by RAPA alters endothelial function by monitoring the effects of topical RAPA ointment on vascular responses to local skin warming (28, 32, 47). Aims will be addressed in healthy human subjects. RAPA ointment will be used to treat skin of one forearm and ointment vehicle will be used to treat the contralateral forearm; thus each subject will be his/her own control. Measurements of RAPA delivery, levels of superoxide and H2O2, bioavailable NO, and endothelial responses to local skin warming will be compared between RAPA-treated and vehicle-treated skin regions to address our aims. Our proposed model will allow us to safely determine the effects of RAPA on vascular function in humans in vivo; an essential prerequisite for translating RAPA into an anti-aging therapy for humans.